The technology described herein relates to a method and an apparatus for generating an encoded output frame. In particular, the technology described herein relates to a method of and an apparatus for generating from a source video frame an encoded output frame to be transmitted to an electronic display for displaying.
As the processing power and speed of portable electronic devices increases, the ability for these devices to handle multimedia correspondingly increases. It has become possible to “stream” multimedia content wirelessly from portable electronic devices to electronic displays, and demand for this is growing. Here, portable electronic devices may for example include mobile telephones (e.g. smart phones), tablet and laptop computers. To “stream” refers to a method of delivering media content in which the content is being received by and simultaneously being displayed on an electronic display continuously while being transmitted from a source such as a portable electronic device.
In such arrangements, source material, such as source video content and/or source graphics content, will typically be processed within a portable electronic device before wireless transmission to the display (e.g. screen). For example, a source video frame may be decoded by a video decoder to obtain a decoded source video frame. The decoded source video frame may then be processed and may furthermore be composited with other content such as a graphics frame to obtain an input video frame, which is to be encoded by a video encoder to obtain an output video frame for transmission to an electronic display.
Conventionally, wireless display protocols specify that the source material is to be converted to a compatible colour space format before being encoded according to a suitable compression standard (e.g. MPEG H 264), and to a predetermined resolution amongst a range of supported resolutions (e.g. from 640×480 up to 1920×1200). The encoded data is packetized and then transmitted wirelessly, for example, over a Wi-Fi ad-hoc network. Common chrominance formats include decimated YUV format (e.g. YUV 4:2:0 format) for video sources and RGB format for graphics and composition sources.
Such processing of source content into encoded data for wireless transmission to a display can require substantial computation resources and bandwidth.
Like reference numerals are used for like features throughout the drawings, where appropriate.